The present invention relates to a self-emptying centrifuge drum with ejection openings which are controlled by an axially movable piston slide, and with inner and outer centering means associated with the piston slide inside the drum, the outer centering means allowing the slide to move axially.
A self-emptying centrifuge drum of this type is known, for example, from German Pat. No. 3 019 737. The piston slide can move axially in the vicinity of both the outer and inner centering means. Since the inner centering means usually has the lower tolerance, it assumes actual guidance of the piston slide. Self-emptying centrifuge drums of the known type are balanced subsequent to assembly to eliminate disequilibriums dictated by the manufacturing process. This leads the piston slide, which is not separately balanced, to acquire its own inherent disequilibrium so that forces will occur during operation that displace the slide to one side inside the drum. The slide will thus come to rest at one side against the inner centering means with a force that is proportional to its inherent disequilibrium, producing frictional forces at this point as the piston slide moves axially. These one-sided frictional forces lead not only to an irregular opening of the ejection openings when the drum empties, but also cause uneven wear on the inner centering means. Since the piston slide lifts only a few tenths of millimeters off the sealing surface during what is called partial emptying, irregular opening leads to non-uniform solids ejection and hence, finally, to dangerous drum disequilibriums.